Fourier Spectroscopy with the Michelson Interferometer


This lab provides the student with an understanding of Fourier spectroscopy, interference, and the Fourier transform. Assessing the success of such an experiment is difficult to do in quantitative terms. Instead, it should be shown that major peaks in the data correspond with accepted literature values of wavelengths. Viewing the spectrums for both sodium and cadmium shows that this experiment achieved much success in predicting major spectral lines. Less success was achieved in confining the wavelength of the HeNe laser to a specific value. Had I been able to take more data, I feel the 632.8 nm peak could have been better identified.

Sources of Error

The error in this experiment most likely resulted from one of two areas. The first is related to apparatus construction. In order to slow the speed of the fringes and decrease the size of the steps taken by the stepper motor a gearing device was constructed. This device was subject to any and probably all human error possible. It was questioned throughout the experiment whether the gearing device was affected the speed of the interference pattern as different parts of the gear came in contact with the motor.

The other large source of error was related to the inability to take data for large amounts of time in order to get more accurate values for the spectral lines. The computer used to take data had problems handling large amounts of data and for that reason, the experiment was limited to taking data for 180 second intervals. Had longer intervals been possible, the Fourier transforms would have almost definitely been more accurate.